Sodium ions and potassium ions are contained in urine, and it is said that a ratio between the sodium ion concentration and the potassium ion concentration is strongly correlated with blood pressure. Accordingly, it is thought that the blood pressure can be easily controlled by measuring the ratio between the sodium ion concentration and the potassium ion concentration in urine (patent document 1).
A method for measuring an ion concentration in a sample solution includes an ion electrode method that measures a change in an electric potential of an electrode in accordance with a change in an ion analyte concentration (to be exact, activity of the ion to be analyzed) in the sample solution through a sensitive part that selectively reacts with the ion analyte and obtains the concentration of the ion analyte in the sample solution.